Man-made landfills are the source of gases which emanate therefrom and pass into the atmosphere. These gases are commonly referred to as "landfill" gases. The major components of landfill gas are methane, carbon dioxide and nitrogen. There are also minor amounts of oxygen, other organic compounds, halides and hydrogen sulfide. Landfill gases which present a potential energy source, presently constitute little more than a nuisance and a potential environmental hazard, and are believed by many scientists to contribute to the greenhouse effect. At present, landfill gas is dealt with by venting to the atmosphere; burning in boilers; flaring; fueling internal combustion engine-driven generators; or as a natural gas substitute after the CO.sub.2 is removed therefrom.
Landfill gas is seen to be a potential source of carbon dioxide, and also as a potential source of natural gas. U.S. Pat. No. 5,059,405 granted Oct. 22, 1991 to R. J. Watson, et al. discloses a process for purification of landfill gas to recover carbon dioxide therefrom. The process described therein involves the removal of impurities such as sulfur compounds, halogens, water, and the like. After removal of the aforesaid impurities, the remaining gas is incinerated in a boiler/incinerator combustion furnace to produce an exit stream of essentially pure carbon dioxide. In this process, the combustible methane component of the landfill gas is simply incinerated.
An article published in the March, 1993 issue of Gas Separation and Purification (Vol. 7, No. 1), pages 31-37 by R. Rautenbach, et al. describes the treatment of landfill gas by converting H.sub.2 S to sulfur in a burner. The sulfur is then transported to a bed of carbon wherein the sulfur is deposited. A problem attendant to this system is that the sulfur can deposit in the transfer lines and can cause a pressure drop in the system to increase. The water in the system is removed by a refrigerator. Halogen compounds are adsorbed on carbon. The carbon is regenerated by steam which results in an environmentally polluting aqueous mixture of water and halogen.